Comment on staff report http://www.straightdope.com/mailbag/mblackice.html
As a lifelong Floridian, I can tell you that we also have something referred to as “black ice” in the vernacular. Florida black ice is not ice at all, but I imagine it is a phenomenon that occurs in any exceptionally warm climate. In the summer time, when temperatures average in the high 90’s, tires on pavement leave a thin coating which, when mixed with oil etc. builds up over time. Normally, our summertime afternoon rain showers clean it off, but in the first few minutes of a rainshower following a dry spell, the roadways become extremely slick and perilous, but only until the rain washes the slick coating off. I know it is not the same thing, but if you ever hear a Southerner talking about “black ice” you will know what they mean.
Note that the Black Ice Staff Report is not officially published yet, but is expected to appear on Tuesday, 8 July 2002. The link in the OP will get you there; and thanks for providing it, goddessodd!
Black Ice is not a common phenomenon in Australia, but we do still get it occasionally at alititude (as many a “Shit! What was that?” will testify to in the Blue Mountains west of Sydney where I learned to drive). My question is this - when water and oil mix (forming the pretty rainbow patterns you sometimes see on driveways when it rains), and this gunk freezes, would this not be even more slippery than your standard black ice?
http://boards.straightdope.com/sdmb/newreply.php
The question I have is, does oil freeze or just increase viscosity? Would the oil, much like a bottle of unmixed salad dressing, float to the surface and lubricate the surface of the ice? On the other hand, if the oil doesn’t freeze, would it prevent the water from freezing completely, resulting in a disgusting sludgey slush? If that were the case, then traction would be improved over black ice. I have only limited experience with artic driving (being a Floridian, of course) but I know that slush is better to drive in than ice. 
Quote from Bibliophage’s staff report:
I’d just like to add that I’ve seen a lot of black ice on lakes (I live in Minnesota) and while it can be very thick, the most common reason for lake ice to look black is that it is dangerously thin.
So if you see some, don’t go a-walkin’ on it (even if you see the local yokels a-drivin’ their pickup trucks on it. And you will.)
There is a legend at Colby College, my alma mater, a small (very white) liberal arts college in Maine. When a prospective professor of Southern heritage came to visit the school, he was led around by the president of the college. The professor asked about winters in Maine, and the president replied “Oh they’re great. You’ll get used to it it no time. Just look out for the black guys.”
“Ummm…Black guys?”
“Yeah, the black guys will get you. You’ll be walking along a path between buildings, then BAM! you’ll be on the ground. Look out for black guys.”
It wasn’t until much later that the professor realized he was being warned about black ice, a phenomenon with which he was unfamiliar.
Black Ice Detector - I wrote a story about two inventors who developed a black ice detector using infrared light. - http://www.geocities.com/lostnprofound/blackice.htm
I’ve never seen enough oil on the road to know (although I might this year, being the proud inheritor of a '68 Mercury), but I can tell you that exhaust fumes can make road ice and snow a lot more slippery. I don’t know if it’s the water vapor or the carbon or both, but if you see a patch of gunky grayish ice, walk around it or coast over it as slowly as you can (if you’re driving, that is).
One caveat not noted by Bibliophage in the original Staff Report concerns the effect of wind. Wind + Black Ice = the notorious and insidious ‘4-wheel drift’; a condition wherein the vehicle is actually sliding sideways while travelling forward. I have had far too much experience driving on black ice and have seen this scenario played out too many times: driver is traveling at a moderate rate of speed, a gust of wind pushes car out of line of travel, driver immediately hits panic button (i.e. brake pedal), vehicle groundloops into the ditch, 23 1/2 hr towing company makes another $200.
I was taught that, should i find myself in the 4-wheel drift situation, to first push in the clutch (or pop the tranny in neutral) to take all driving force off the wheels. Then to ease the vehicle back to the desired path and finally to allow the vehicle to slow considerably before engaging the engine. Above all else, never touch the brakes.
Surprisingly, the car that i found was least affected by black ice was a Honda CRX. My brother and i once had to travel 150 miles on black ice with gusting winds. I was driving the CRX and he had a 3/4 ton 4-wheel drive pickup. I had to slow from 45mph (a speed that was causing me no grief what-so-ever) to 25mph as he was complaining that his truck was a bit ‘squirrely’ above 25. Must be the aerodynamics of the CRX.
Another Minnesotan here, and I can personally testify that not all black ice is clear. In fact, much of it is actually black. The ice that I speak of is often found in high traffic areas, particularly at stop lights where cars have longer to sit and idle. The exhaust emissions combine with the existing snow and water vapor, they get packed down, and an ice eventually made that is as dark and glossy as obsidian.
It’s incredibly splippery. And, upon appraching a stop light in winter, there aren’t many faster ways to go from ho hum to holy shit!
Wow—what a pleasant surprise to receive an email from C K Dexter Haven saying my question had been addressed. Thanks. It looks like there’s a very lively community here and I look forward to exploring it further. Just a couple of things I’d like to clarify.
Ah. Actually, I was born in Michigan, and learned to drive there. Michigan is known for, among other things, harsh winter driving conditions. It is also known as the automotive capital of the world. Thus, Michiganders not only know their weather, but tend to be very informed and able drivers in adverse conditions. Heck, my grandmother has no problem recovering from a skid on an icy roadway, and this is AFTER her stroke.
My point is that Michiganders, in general, are particularly critical of other peoples’ driving. If we see a one-car accident, we’re less likely to blame road conditions for the mishap, and more likely to ascribe such minor calamities to conditions like “driver idiocy.”
The last part of my question remains unanswered. “Does [black ice] really cause all the accidents attributed to it?” I mean, when filling out their accident reports, do police investigators actually write the words “black ice” under “cause of accident?” For that matter, do auto insurers make a claims distinction between encounters with black ice and driver error?
We get black ice here in California. My commute involves a windy road into a bit of a valley with a canopy of trees overhead. It’s not uncommon to find small patches of black ice that have eluded the sun’s attention after a freezing winter night. Never encountered it personally but plenty of others here at work have.
I also live in Michigan and the other winter road hazzard that Michigan is known for is rock salt. Most of the other locals mentioned don’t use it or don’t use it in the huge heaping piles that Michigan does. Therefore less black ice. Also Michigan rarely sees temperatures below the range where salt tends to work because of the moderating effects of the Great Lakes.
I have also lived in Wyoming where the cure for ice or snow covered roads, even in town, was commonly known as “spring.” I saw a great deal of black ice out there, especially on bridges and mountain passes. The problem with black ice is that it looks just like the surrounding damp pavement. Especially on a curve this can be quite a shock.
I even saw an instance in Michigan not too long ago driving up I-96 heading north from Metro Airport. It had been a rain/snow mix for most of the day. Just after sunset the air temps dropped just low enough that all of the overpasses froze within about 15 min. People who had been driving on damp roadways without a problem all day were suddenly hitting patches of ice whenever they went over a bridge. I must have seen 30 - 40 vehicles off the road in 60 miles or so. It does happen even in Michigan.
Nice columnm, I just have a note about metrics on behalf of the rest of the world: please, please, if you have to use the Fahrenheit scale, provide Celsius figures in brackets or something.
Good point, Abe. I’ll do that in the future.
And while you’re at it, could you provide Kelvin temperatures too? They’re ever so much more convenient for thermodynamic calculations. 
– tracer, setting his thermostat to 298 degrees.